"….she needs to be able to beg Voldemort for Harry’s life, she needs to think he might die, and you’re the worst spoiler in the world that didn’t turn out to be true…."
-- Scorpius Malfoy (CC4.5)
31 October 1981
Needing to warn his father Harry quickly about Delphi’s plan to kill him, Albus Potter and Scorpius Malfoy are waiting and watching in Godric’s Hollow outside Lily and James Potter’s house. They discuss possible ways of telling his father where they are, including trying to pre-warn the still alive Albus Dumbledore (CC4.5).
Scorpius and Albus see Lily take baby Harry out in his pram. Albus has the idea that the way to send his father a message in the future is via the old blanket that Lily uses to cover Harry as a baby (CC4.5), which Albus had rejected at the start of the school year (CC1.7).
All Hallow's Eve - 31st October 1981
This event takes place during the Voldemort Final timeline, as described in the essay "Albus Potter and the lesson in Quantum Mechanics" by Nick Moline.
In spite of the fix they are in, there is still some humour to be found in their situation, including the idea of trying to send a subliminal message via baby Harry by shouting at him. But even if they try to hide for forty years to be able to warn the Wizarding World, Delphi would probably track them down first.
"Still, if I had to choose a companion to be at the return of eternal darkness with, I'd choose you."
"No offence, but I'd choose someone massive and really good at magic."
-- Scorpius Malfoy and Albus Potter (CC4.5)
Albus sees his grandmother Lily tucking baby Harry in with the baby blanket: "Look at the love with which she's put it on him - I think he'd like to know about that - I wish I could tell him." He then remembers about how Love Potions work and how he and Scorpius could use it. Not all their school lessons were unsuccessful after all (CC4.5).
From the Web
Pottermore: Harry Potter and the Cursed Child
The theatre production opened in the West End of London at the Palace Theatre on 31 July 2016, with Sam Clemmett in the role of Albus Potter, Anthony Boyle as Scorpius Malfoy and Annabel Baldwin as Lily Evans Potter: Harry Potter and the Cursed Child, Parts One and Two